createStore(reducer, preloadedState, enhancer)

Creates a Redux store that holds the complete state tree of your app.
There should only be a single store in your app.

If using createStore directly, it will not be threadsafe.

It is STRONGLY recommended that createThreadSafeStore() is used unless there is good reason to do otherwise.

The rest of this doc applies to all createStore functions.

Arguments

  1. reducer (Reducer): A reducing function that returns the next state tree, given the current state tree and an action to handle.

  2. [preloadedState] (State): The initial state. You may optionally specify it to hydrate the state from the server, or to restore a previously serialized user session.

  3. [enhancer] (StoreEnhancer): The store enhancer. You may optionally specify it to enhance the store with third-party capabilities such as middleware, time travel, persistence, etc. The only store enhancer that ships with Redux is applyMiddleware().

Returns

(Store): An object that holds the complete state of your app. The only way to change its state is by dispatching actions. You may also subscribe to the changes to its state to update the UI.

Example

fun todosReducer(state: List<Todo>, action: Any) =
    when (action) {
        is AddTodo -> state.plus(Todo(action.text))
        is ToggleTodo -> state.mapIndexed { index, todo ->
            if (index == action.index) {
                todo.copy(completed = !todo.completed)
            } else {
                todo
            }
        }
        else -> state
    }

val store = createStore(::todosReducer, AppState.INITIAL_STATE)


fun main() {
    store.dispatch(AddTodoAction(text = "Read the docs"))

    logger.debug(store.state)
    // AppState(list = [ 'Use Redux', 'Read the docs' ])
}

Tips

  • Don't create more than one store in an application! Instead, use combineReducers or combine your reducers in code to create a single root reducer out of many.

  • It is up to you to choose the state format and structure. Data classes work well as they have toString() and copy(). Also use immutable val rather than var except where unavoidable.

  • For universal apps that run on the server, create a store instance with every request so that they are isolated. Dispatch a few data fetching actions to a store instance and wait for them to complete before rendering the app on the server.

  • When a store is created, Redux dispatches a dummy action to your reducer to populate the store with the initial state. You are not meant to handle the dummy action directly.

  • To apply multiple store enhancers, you may use compose().

← API ReferencecreateThreadSafeStore →